WHY MEN DO NOT FALL OFF.
We come now to a curious thought.
The world is a round ball; and people live on all parts of it.
Therefore, a man on the opposite side from us stands with his feet
turned upwards towards our feet and his head pointing in the other
direction--“hanging downwards, in short,” you might say.
This seems extremely odd.
Suppose you hold a big ball, and place a pea on the top of it. The pea
will stay where you put it, if you keep your hand steady. But if you
place the pea at the side or bottom of the ball it will instantly drop
away. Try for yourself, and you will see.
To be sure, a fly or a spider might stand with equal ease on the top
or the bottom of the ball. The feet of a fly and a spider are made for
clinging and walking in such a position. Man is not formed to stand or
walk upside down, like a fly on the ceiling.
Now, why don’t the people on the other side of the world, in Australia
for instance, drop off the earth, and fall away into the sky?
Of course there is a sky under our feet, just as much as over our
heads. The entire world is surrounded on all sides by sky; not only
over our heads, but down under our feet, beyond the solid Earth on
which we stand, and in all directions.
If you were to travel round the world, and were to reach
Australia--then, as you stood on the ground, your feet would point
upwards to the feet of people in the United States; just as two flies,
standing on two opposite sides of a ball, have their feet pointed,
those of one fly towards those of the other. It cannot help being so,
because of the shape of our Earth.
How do you think you would feel there? Do you think you would be in
danger of dropping off the Earth into the blue sky?
Not in the least. No more danger of such an accident in Australia than
in America. Nothing indeed would astonish you more! Instead of being
disposed to fall from the Earth, you would find it every inch as hard
there as here to get away from the Earth. Your own weight would hold
you fast to the ground in Australia just the same as in America.
Try to jump up into the air, with all your strength. Try your very
utmost; get as far away as you can from the ground, and stay up in the
air as long as possible.
Not much good; is it? Do what you will, you do not find that you can
rise more than a foot or two, and you instantly drop back again. The
most powerful leaper can manage at most only a few feet. A man is quite
unable to stay up in the air at all, unless something holds him there:
far less is he able to drop or float away into the sky.
And the reason why he cannot is that he is too heavy. He is too heavy
in America: and he is too heavy in Australia. In both cases he is
heavy _towards the ground_: and he cannot get away from the ground
without something to bear him up. It is just as impossible that people
in Australia should drop off the world into the sky as that people in
America should do so.
But--you will perhaps say--the sky is _above_ us here; and in Australia
it would be _under_ us.
Oh, no; it would not! The sky is all round the whole Earth, on every
side alike. In all parts of the world people have the sky over their
heads and firm ground beneath their feet.
The Australian sky is under the feet of those who live in North
America: that is true. But then it is no less true that the North
American sky is under the feet of those who live in Australia. To you
the Earth is underneath: the sky is overhead. To an Australian also the
Earth is underneath and the sky is overhead. All round the world it is
the same. _Down_ means always towards the ground. _Up_ means always
towards the sky.
If you hold up a stone in the air, and let it go, what happens? The
stone drops at once to the ground.
If you fling a ball into the air, what happens? The ball goes a little
upwards, carried by the force of your fling: but soon it curves over
and comes to the ground.
If you tilt up a jug full of water, what happens? The water pours down
upon the floor.
If a man steps over a precipice-edge, what happens? He falls to the
bottom, and is most likely killed.
But these things are not more true of the United States than of
Australia. All round the world, in every part, it is the same. Water
always flows downward. Loose bodies always drop downward, unless kept
up by something.
We have been asking why it is that people never drop off from the Earth
into the sky. Of course nobody ever asks that question about the part
of the Earth on which he happens to be. Whether he is in England, or in
America, or in Australia, he knows very well that _he_ is in no danger
of “dropping off.” The very idea as to himself would seem absurd. To
“drop off” would really be to rise upward into the sky: and he feels
that he is much too heavy for that. It is only when he thinks about
the other side of the world, and about people walking there with their
heads hanging downward----
But they do _not_ walk with their heads hanging downward. Their heads,
like ours, point upward to the sky; and their feet, like ours, rest
firmly on solid ground; and they too, like us, are heavy towards the
Earth. It is as impossible for a man in Australia as for a man in
England or America to “drop off” the Earth--in other words, to rise
upwards towards the sky. His own weight holds him down.
What do we mean by “weight?” What makes a man “heavy?”
He is made heavy by the Earth’s pulling or attracting him; and this
gives him weight.
And how does the Earth pull?
There I cannot tell you much. We know that the Earth does pull: but how
she pulls is another question. We name that pulling “Attraction,” and
sometimes we call it by a longer word, “Gravitation.” But not the very
wisest man living can explain to us exactly what attraction _is_. He
can only tell us what it _does_.
Did you ever see a magnet? It is generally shaped rather like a
horse-shoe: and the two ends have an odd drawing power. A number of
tiny iron shavings, held near enough, will jump up to meet the magnet
as if they were alive. This is because the magnet pulls them towards
itself. Sometimes a toy-box of metal ducks or fishes is sold, with a
magnet; and they will follow the magnet to and fro, in a basin of water.
Now our Earth seems to be a sort of huge magnet, with power to pull
towards herself, not only iron or steel, but every single thing and
creature upon her surface. Not only on one side of the Earth, but
around the whole globe, on every part, there is the same steady
downward drag, always _toward the centre of the Earth_.
The mountains are pulled earthward: so are houses and trees, rocks and
soils, seas and rivers, animals and men. There is not a single thing on
or near the surface of our Earth which is not thus drawn earthward.
If it were not for this attraction nothing would have any weight. When
you leap upward and instantly drop back it is because the Earth drags
you down. Without such dragging you would not be heavy at all.
Think what that would mean. You might jump over the highest mountains
with ease: or you might spring away into the sky, and never return:
only, of course, there is no air, far away in the sky, and you could
not breathe without air.
But if the Earth did not attract we should have no air here either,
because it would long ago have all wandered away. Earth’s strong
attraction holds the air prisoner, as well as all other things upon her
surface.
Now do you begin to see how it is that people do not fall away into
the sky, from any part of Earth? They are held firmly down by Earth’s
perpetual drag, which gives them weight. Whether they are in England or
in Australia, in Asia or in America, makes no difference. The _pull_ is
always downward, always earthward. The difficulty always is to get away
from earth, upward, toward the sky.
So when we think of the world as a whole we have to remember that in
the surrounding sky there is no true “up” or “down” in one direction
more than another. “Up” is towards the sky for each man, from that part
of Earth on which he stands: and as our Earth is ever turning round and
round our “up” is constantly changing its direction.
Perhaps you will think that I am rather slow in getting to my subject
of “The Starry Skies.” Two whole chapters first about this old Earth of
ours!
But indeed I have not been slow: for on the very first page we started
right off with a Bright World in the Sky.
By this time you know that our world is actually in the sky, just as
much as the sun and moon are in the sky. We are in the moon’s sky, and
in the sun’s sky, and in the sky of all other planets and all other
stars. For our Earth floats in the same boundless sky-depths as all of
them, those sky-depths which are usually known by the name of _Space_.
So now, when “Space” is spoken of, you will understand. You will know
that it means the Sky, in which float all the heavenly bodies.
“Only”--you will perhaps say--“the Moon and the Sun are bright; and so
are the Stars. But our dull old world is not bright at all.”
That is a great mistake, I assure you. Our world is very bright indeed.
She shines with an exquisite radiance. Not indeed with such a dazzling
glory as the Sun, but quite as brightly as the Moon.
Have you ever noticed how the ocean shines, and flashes forth light,
when the Sun beats down full upon it? Or, again, have you not been
struck with the shining of white clouds in sunlight? More or less the
whole surface of our Earth catches and gives forth again the brightness
that comes to her from the Sun.
If we could travel away from the Earth to a good distance--say, as
far as to the Moon--we should see the round Earth like an enormous,
brilliant Moon in the sky, only far larger and more beautiful than our
Moon ever looks to us. Some parts would be darker, some more shining;
but as a whole the Earth would be a splendid sight.
Not bright? Yes, indeed; we are living on a very bright world indeed,
though we cannot always see her radiance.
QUESTIONS.
1. What is Space?
By Space we mean Sky--the whole great Sky, in which are all the
heavenly bodies.
2. Is our Earth in the Sky?
Just as truly as the Sun and Moon are in the Sky. They are in our sky,
we are in their sky.
3. Does our Earth float in Air?
No; she floats in the Sky: and the air is a part of the Earth.
4. Do people on the other side of the globe walk head downwards?
No; they walk as we do, on firm ground, with the Sky over their heads.
5. What is meant by “up” and “down” to us on Earth?
On every part of the Earth _up_ is always toward the Sky, and _down_ is
always toward the Earth.
6. Give some examples of the way in which all things move earthward.
Water always pours downward. A stone flung, or a ball dropped, always
reaches the ground.
7. Why do things descend thus?
Because of their own weight or heaviness.
8. What causes weight?
The pull of the earth.
9. Give two other names for that “pull.”
Attraction and Gravitation.
10. Tell me a few things that are pulled earthward.
Men, animals, trees, houses, rocks, cities, hills, mountains, lakes,
rivers, oceans, air, clouds, etc.
11. What keeps people on the other side of the Earth from dropping off
into the sky?
They cannot possibly drop off; because the sky there is upward, the
same as here.
12. What would “dropping off” really be?
It would be rising upward into the sky.
13. Why should a man not rise upward?
He cannot, because he is too heavy.
14. He is heavy towards what?
He is heavy towards the Earth, because of the Earth’s attraction.
15. Is he as heavy in Australia as in the United States?
Exactly the same.
16. In what direction is he pulled there?
Towards the Earth. All round our whole world the pull is towards the
centre of the Earth.
17. Can our Earth be called “a bright world?”
Quite as much so as other planets. If we were far enough off she would
be seen by us to shine with reflected sunlight, like the Moon.